Settable composition containing potassium chloride

ABSTRACT

The present invention relates to settable compositions for general purpose concrete construction containing Class-F fly ash, Class-C fly ash and/or slag, and potassium chloride (KCl) as a substantial replacement for Portland cement conventionally used in such compositions. The potassium chloride is an additive for improved high early strength and accelerated setting times, thereby allowing the concrete structure to be put into service sooner, reducing labor cost, and allowing precast concrete and concrete masonry manufacturers to achieve rapid form and mold turnover.

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/982,854, filed Oct. 22, 2001 now U.S. Pat. No. 6,656,264.

FIELD OF THE INVENTION

The present invention relates to the field of settable compositions forgeneral purpose concrete mixes, and more particularly to settablecompositions containing additives for improved strength and shortenedsetting times.

BACKGROUND OF THE INVENTION

The present invention is concerned with the utilization of potassiumchloride (KCI) as an additive for improving the one-day strength and forshortening the setting times of concrete mixes. Further, the inventionis also concerned with the utilization of three industrial by-products;namely, Class-F fly ash, Class-C fly ash, and blast furnace slag ingeneral purpose concrete-making compositions.

When finely divided or pulverized coal is combusted at hightemperatures, for example, in boilers for the steam generation ofelectricity, the ash, consisting of the incombustible residue plus asmall amount of residual combustible matter, is made up of twofractions, a bottom ash recovered from the furnace or boiler in the formof a slag-like material and a fly ash which remains suspended in theflue gases from the combustion until separated therefrom by knownseparation techniques, such as electrostatic precipitation. This fly ashis an extremely finely divided material generally in the form ofspherical bead-like particles, with at least 70 percent by weightpassing a 200 mesh sieve, and has a generally glassy state resultingfrom fusion or sintering during combustion. As recognized in theAmerican Society of Testing Materials (ASTM) specification designationsC618-00 entitled “Fly Ash and Raw or Calcined Natural Pozzolan for Useas a Mineral Admixture in Portland Cement Concrete” and D5370-96entitled “Standard Specification for Pozzolanic Blended Materials inConstruction Application,” fly ash is subdivided into two distinctclassifications; namely, Class-F and Class-C. The definitions of thesetwo classes given in the aforementioned ASTM specifications are asfollows:

“Class-F—Fly ash normally produced from burning anthracite or bituminouscoal that meets the applicable requirements for this class as givenherein. This class fly ash has pozzolanic properties.

Class-C—Fly ash normally produced from lignite or subbituminous coalthat meets the applicable requirements for this class as given herein.This class of fly ash, in addition to having pozzolanic properties, alsohas some cementitious properties. Some Class-C fly ashes may containlime contents higher than 10 percent.”

The latter reference to “pozzolanic properties” refers to the capabilityof certain mixtures that are not in themselves cementitious, but arecapable of undergoing a cementitious reaction when mixed with calciumhydroxide in the presence of water. Class-C fly ash possesses directcementitious properties as well as pozzolanic properties. ASTM C618-00is also applicable to natural pozzolanic materials that are separatelyclassified as Class N but are not pertinent here.

As the above quotation from the ASTM specification indicates, the typeof coal combusted generally determines which class fly ash results, andthe type of coal in turn is often dependent upon its geographic origin.Thus, Class-C fly ash frequently results from the combustion of coalsmined in the Midwest United States; whereas Class-F fly ash often comesfrom combustion of coals mined in the Appalachian region of the UnitedStates. The ASTM specification imposes certain chemical and physicalrequirements upon the respective fly ash classifications which are setforth in U.S. Pat. No. 5,520,730, the disclosure of which isincorporated herein by reference.

Blast furnace slag is a by-product of the production of iron in a blastfurnace; silicon, calcium, aluminum, magnesium and oxygen are the majorelemental components of slag. Blast furnace slags include air-cooledslag resulting from solidification of molten blast furnace slag underatmospheric conditions; granulated blast furnace slag, a glassy granularmaterial formed when molten blast furnace slag is rapidly chilled as byimmersion in water; and pelletized blast furnace slag produced bypassing molten slag over a vibrating feed plate where it is expanded andcooled by water sprays, whence it passes onto a rotating drum from whichit is dispatched into the air where it rapidly solidifies to sphericalpellets. In general the glass content of the slag determines thecementitious character. Rapidly cooled slags have a higher glass contentand are cementitious; slowly cooled slags are non-glassy and crystallineand, thus do not have significant cementitious properties.

The quantities of these by-product materials that are produced annuallyare enormous and are likely only to increase in the future. As petroleumoil as the fuel for the generation of electricity is reduced because ofconservation efforts and unfavorable economics, and as politicalconsiderations increasingly preclude the construction of new nuclearpower electrical generating facilities, or even the operation orcontinued operation of already completed units of this type, greaterreliance will necessarily fall on coal as the fuel for generatingelectricity. As of 1979, the volume of Class-F fly ash that wasavailable then was estimated to be about five times what could bereadily utilized. The estimated annual total production of coal ash inthe U.S. is about 66.8 million tons, while the annual total coal ashsales in the U.S. is only about 14.5 million tons. Further, in Canada,the recovery of copper, nickel, lead and zinc from their ores producesover twelve million tons of slag per year, which is usually accumulatednear the smelters with no significant use. Obviously, there is an urgentand growing need to find effective ways of employing these unavoidableindustrial by-products since they will otherwise collect at a staggeringrate and create crucial concerns regarding their adverse environmentaleffects.

Various proposals have already been made for utilizing both types of flyash. According to Lea (1971), The Chemistry of Cement and Concrete,Chemical Publishing Company, Inc., page 421 et seq., fly ash, i.e.,Class-F type, from boilers was first reported to be potentially usefulas a partial replacement for Portland cement in concrete constructionabout 50 years ago, and its utilization for that purpose has sincebecome increasingly widespread. It is generally accepted that theproportion of Portland cement replaced by the usual fly ash should notexceed about 20 percent to avoid significant reduction in thecompressive strength of the resultant concrete, although some morecautious jurisdictions may impose lower limits, e.g., the 15 percentmaximum authorized by the Virginia Department of Highways andTransportation (VDHT). As described in Lea on page 437, the substitutionof fly ash tends to retard the early rate of hardening of the concreteso that the concrete exhibits up to a 30 percent lower strength afterseven days testing and up to a 25 percent lower strength after 28 daysof testing, but in time the strength levels normalize at replacementlevels up to 20 percent. Increasing the substitution quantity up to 30percent gives more drastic reduction in the early compression values aswell as an ultimate strength reduction of at least about 15 percentafter one year.

The limited substitution of fly ash for Portland cement in concreteformulations has other effects beyond compressive strength changes, bothpositive and negative. The fly ash tends to increase the workability ofthe cement mix and is recognized as desirably reducing the reactivity ofthe Portland cement with so-called reactive aggregates. On the otherhand, fly ash contains a minor content of uncombusted carbon that actsto absorb air entrained in the concrete. Because entrained air desirablyincreases the resistance of the hardened concrete to freezing, suchreduction in entrained air is undesirable, but can be compensated for bythe inclusion as an additive of so-called air-entraining agents.

Dodson, et al. in U.S. Pat. No. 4,210,457, while recognizing theaccepted limit of 20 percent replacement with fly ash of the Portlandcement in concrete mixes, proposes the substitution of larger amounts,preferably 50 percent or more, of the Portland cement with particularselected fly ashes having a combined content of silica, alumina andferric oxide content, less than 80 percent by weight, and a calciumoxide content exceeding 10 percent, based on five samples of such ashes,varying from about 58-72 percent combined with a calcium oxide range ofabout 18-30 percent. Six other fly ash samples that are not suitable atthe high replacement levels of 50 percent or more were shown to vary inthe combined oxide content from about 87-92 percent and in calcium oxidecontent from about 4 percent to about 8 percent. Evaluating these valuesagainst the ASTM C618-00, one observes that the acceptable fly ashescome under the Class-C specifications, while the unacceptable ashes fellwithin the Class-F specification. Thus, Dodson, et al. in effectestablish that Class-C fly ashes are suitable for substantially higherlevels of replacement for Portland cement in concrete mixes than areClass-F fly ashes, and this capacity is now generally recognized, withClass-C fly ashes being generally permitted up to about a 50 percentreplacement level while maintaining the desirable physical properties ofthe concrete, especially compressive strength.

In U.S. Pat. No. 4,240,952, Hulbert, et al. while also acknowledging thegenerally recognized permissible limit of Class-F fly ash replacementfor Portland cement of 20 percent, propose replacement of at least 50percent and up to 80 percent, provided the mix contains as specialadditives about 2 percent of gypsum and about 3 percent of calciumchloride by weight of the fly ash. The fly ash described for thispurpose, however, was a Class-C fly ash analyzing about 28 percentcalcium oxide and combined silica, alumina and ferric oxide content ofabout 63 percent. With up to 80 percent of this fly ash and thespecified additives, compressive strengths comparable to straightPortland cement were said to be generally achievable. In one exampleusing 140 pounds Portland cement and 560 pounds of fly ash (20:80 ratio)with conventional amounts of coarse and fine aggregate, and water andincluding the requisite additives, compressive strengths tested at 3180psi for 7 days, 4200 psi for 14 days and about 5000 psi at 28 days.

In U.S. Pat. Nos. 4,018,617 and 4,101,332, Nicholson proposed the use ofmixtures of fly ash (apparently Class-F in type), cement kiln dust andaggregate for creating a stabilized base supporting surface replacingconventional gravel or asphalt aggregate stabilized bases in roadconstruction wherein the useful ranges were fly ash 6-24 percent, CKD(cement kiln dust) 4-16 percent and aggregate 60-90 percent, with 8percent CKD, 12 percent fly ash and 80 percent aggregate preferred.Compressive strength values for such measures as revealed in theexamples varied rather erratically and generally exhibited only smallincreases in compressive strength over the 7 to 28 day test period.Among the better results were for the preferred mixture wherein thevalues increased from about 1100 psi at 7 days to 1400 psi at 28 days.The addition of a small amount of calcium chloride improved those valuesby about 200 psi. On the other hand, the addition of 3 percent of limestack dust recovered from a lime kiln significantly reduced the resultsto about 700 psi at 7 days to 900-1300 psi at 28 days. Elimination ofthe aggregate reduced the strength to a fraction of the values otherwiseobtained, a mixture of 12 percent CKD and 88 percent fly ash aloneshowing strength values of only about 190-260 psi over the 28-day testperiod. Similarly, the choice of a finely divided aggregate such as fillsand resulted in about the same fractional level of strength values inthe range of about 140-230 psi. A combination of finely divided andcoarse aggregate in approximately equal amounts reduced the compressivestrength values by about 50 percent with virtually no change over thetest period, giving values ranging from 650-750 psi, except where 1percent of Type 1 Portland cement was included which restored thestrength values to about their original level, except at the initial 7days period where the strength values were about 800-900 psi, increasingat 28 days to about 1200-1600 psi. Curiously, the best strength resultswere attained when 11.6 percent fly ash was combined with 3.4 percentlime with the balance crushed aggregate, the CKD being omitted entirely,for which the strength values while starting at a lower level of about850-950 at 7 days increased to about 1700 psi at 28 days.

The combination of fly ash and lime stack dust incidentally mentioned inthe later patent was explored further by Nicholson in U.S. Pat. No.4,038,095 which concerns mixtures of about 10-14 percent fly ash, about5-15 percent lime stack dust with the balance aggregate in the range of71-85 percent. Somewhat inexplicably, the compressive results reportedhere for such mixtures do not reach the high level specified in thefirst two aforementioned Nicholson patents, the strength valuesspecified being only about 1000 psi with the more general levels wellbelow that depending on particular proportions.

In U.S. Pat. No. 4,268,316, Wills, Jr. discloses the use of mixtures ofkiln dust and fly ash as a replacement for ground limestone and gypsumfor forming a mortar or masonry cement, using proportions of about 25-55percent Portland cement, about 25-65 percent CKD and 10-25 percent flyash. When these mortar formulations were mixed with damp sand in theproportions of about one part cement mixture to 2.5-3 parts sand,compression strengths comparable to those of standard masonry cementcomposed of 55 percent cement clinkers, 40 percent limestone and 5percent gypsum were shown for mixtures containing 50 percent cement,24-40 percent CKD and 15-25 percent fly ash. Inexplicably, in oneexample, when the cement content was increased to 55 percent with 35percent CKD and 10 percent fly ash, the compressive strengths dropped byabout 30-40 percent at both the 7 day and 28 day ages to levels inferiorto the standard material. As the cement content was decreased, withcorresponding increases in the CKD, the compressive strength valuesdropped drastically. On the other hand, in another similar example,mixtures containing 55 percent cement, 35 percent CKD and 10 percent flyash proved superior in compressive strength, particularly at the 28 dayage, to mixtures containing 50 percent cement, 35 percent fly ash and 15percent CKD, as well as other standard masonry cements containing 50percent cement, 47 percent limestone and 3 percent gypsum. Indeed,strength values dropped about 40 percent for the mixtures having a 5percent reduction in cement and a corresponding 5 percent increase inthe fly ash to values definitely inferior to the standard cements.Similar variations were shown under laboratory test conditions forcomparable 50/35/15 mixtures dependent on the source of the fly ashwhile under actual construction conditions for the same mixtures,compressive strength values were reduced by about 50 percent for boththe conventional masonry cement containing 55 percent Portland cementand comparable mixtures within the patented concept. The fly ash herewas preferably Class-F with Class-C materials being less desirable.

In U.S. Pat. No. 4,407,677, Wills, Jr. went on to teach that in themanufacture of concrete products such as blocks or bricks, the fly ashusually employed in combination with Portland cement therein could bereplaced in its entirety by CKD with modest improvement in earlycompressive strength values for such products. Thus, at one-day andtwo-day tests compressive strength values of about 500-800 psi wereshown, but were said to increase to about 1200 psi after 28 days. Themixes disclosed in Wills, Jr. '677 contained 0.4-0.9 parts cement, about0.1-0.6 parts CKD and 10-12 parts aggregate combining both fine andcoarse materials, such as expanded shale and natural sand in a weightratio of 80/20. Masonry cements generally develop at least about 95percent of their strength properties at 28 days age so that additionalaging of the patented products would not be expected to result in anysignificant increase in their compressive strength values.

U.S. Pat. Nos. 5,520,730 and 5,266,111 of the present inventor, disclosea general purpose concrete composition comprising Portland cement,Class-F fly ash, and CKD. The patents also disclose a “synthetic Class-Cfly ash blend” comprising Class-F fly ash and CKD. These patentsdisclose the advantages of early strength of concrete; however,utilization of potassium chloride as a cement additive is not disclosed.

In U.S. Pat. No. 5,032,181, Chung discloses a carbon reinforced cementthat displays high tensile and flexural strengths. During thefabrication of the cement, an accelerating agent mixture is also added.The accelerating mixture comprises polyethanolamine plus either (1)metal sulfate and metal aluminum sulfate, or (2) metal nitrite and metalchloride. The metal sulfate can be potassium sulfate; and the metalchloride can be potassium chloride. There is no disclosure in the patentregarding the one-day strength of the disclosed general purpose concretecompositions.

None of the above patents addresses the issue of early strength andsetting times of concrete; therefore, there remains a need for concretemixes with high early strength and fast setting times, because theaddition of fly ash to concrete often results in slow setting. There aremany advantages for having high early strength and fast setting times,such as allowing the concrete structure to be put into service sooner,thereby reducing labor cost, and allowing precast concrete and concretemasonry manufacturers to achieve rapid form and mold turnover.

SUMMARY OF THE INVENTION

An advantage of the present invention is to provide a settablecomposition for improved early strength comprising cement and potassiumchloride. In a preferred embodiment, the cement is present in an amountgreater than about 50 percent by weight, the potassium chloride ispresent in an amount of about 1 percent to about 5 percent by weight.

A further advantage of the present invention is to provide a settablecomposition for improved early strength comprising cement, Class-F flyash, and potassium chloride. In a preferred embodiment, the cement ispresent in an amount greater than about 50 percent by weight, theClass-F fly ash is present in an amount of about 20 percent to about 30percent by weight, and the potassium chloride is present in an amount ofabout 1 percent to about 5 percent by weight.

A further advantage of the present invention is to provide a settablecomposition for improved early strength comprising cement, Class-C flyash, and potassium chloride. In a preferred embodiment, the cement ispresent in an amount greater than about 50 percent by weight, theClass-C fly ash is present in an amount of about 20 percent to about 30percent by weight, and the potassium chloride is present in an amount ofabout 1 percent to about 5 percent by weight.

A further advantage of the present invention is to provide a settablecomposition for improved early strength comprising cement, Class-C flyash, Class-F fly ash, and potassium chloride. In a preferred embodiment,the cement is present in an amount greater than about 50 percent byweight, the Class-C fly ash is present in an amount of about 10 percentto about 20 percent by weight, the Class-F fly ash is present in anamount of about 10 percent to about 20 percent by weight, and thepotassium chloride is present in an amount of about 1 percent to about 5percent by weight.

A further advantage of the present invention is to provide a settablecomposition for improved early strength comprising cement, slag, andpotassium chloride. In a preferred embodiment, the cement is present inan amount greater than about 50 percent by weight, the slag is presentin an amount of about 20 percent to about 50 percent by weight, and thepotassium chloride is present in an amount of about 1 percent to about 5percent by weight.

Methods of making concrete from the above compositions are alsodisclosed.

DETAILED DESCRIPTION OF THE INVENTION

Several different types of Portland cement are available and all areuseful with the present invention. Type I is the general purpose varietyand is most commonly employed, but Type III can also be used for theearly strength application of the present invention. Commercial blendedcements, such as Type I-P, wherein 20 percent Class-F fly ash is blendedwith 80 percent by weight Portland cement clinker during pulverizationshould be avoided.

Any standard or common Class-F fly ash obtained from boilers and likefurnaces used for the combustion of pulverized coal, particularly of abituminous or anthracite type, and especially from coal-fired,steam-generating plants of electrical utilities, is suitable for use asthe Class-F fly ash component of this invention. Such fly ash shouldhave a combined silica, alumina and ferric oxide content of at leastabout 70 percent and preferably 80 percent or higher by weight and alime (CaO) content below about 10 percent, usually about 6 percent byweight or less.

Any standard or common Class-C fly ash obtained from the burning oflignite or subbituminous coal is suitable for use as the Class-C fly ashcomponent of this invention. Such Class-C fly ash generally containsmore calcium and less iron than Class-F fly ash and has a lime contentin the range of 15 percent to 30 percent.

Likewise, any blast furnace slag is appropriate for the presentinvention. Slag is a non-metallic coproduct produced in the productionof iron in a blast furnace. It consists primarily of silicates,aluminosilicates and calcium-alumina-silicates. The molten slag usuallycomprises about twenty percent by mass of iron production. Differentforms of slag products are produced depending on the method used to coolthe molten slag. These products include air-cooled blast furnace slag,expanded or foamed slag, pelletized slag, and granulated blast furnaceslag. Granulated blast furnace slag satisfying the ASTM 989specification is preferred.

Any potassium chloride is appropriate for the present invention.Potassium chloride is a ubiquitous salt generally occurring as a whitegranular powder or colorless crystal. Commercially, potassium chlorideis available in a wide range from pharmaceutical grade to potash (about96 percent KCI) for fertilizer. Although any potassium chloride isappropriate for the present invention, cost is a major considerationbecause potassium chloride is available in many grades. Therefore, theleast expensive form of potassium chloride that is effective for thepresent invention is most preferred.

As will be established hereinafter, within the above limits for thecompositions of the invention, the concretes produced therefrom exhibitsubstantially comparable or superior properties for use in generalpurpose cement construction, especially one-day compressive strength tocorresponding all Portland cement mixes.

Concrete mixes using the present invention may also contain aggregatematerials. The choice of aggregate material for concrete mixes using thepresent blends will pose no problem to the person skilled in the designof such mixes. The coarse aggregate should have a minimum size of about⅜ inch and can vary in size from that minimum up to one inch or larger,preferably in gradations between these limits. Crushed limestone, graveland the like are desirable coarse aggregates, and the material selectedin any case should exhibit a considerable hardness and durabilityinasmuch as crumbly, friable aggregates tend to significantly reduce thestrength of the ultimate concrete. The finely divided aggregate issmaller than ⅜ inch in size and again is preferably graduated in muchfiner sizes down to 200-sieve size or so. Ground limestone, sand and thelike are common useful fine aggregates.

In accordance with the present invention, silica fume can also be addedto the cement mixture to achieve high strength and chloride protectionfor the concrete. Silica fume is preferably used from 3-12 percent ofthe amount of cement that is being used in the mixture.

Other additives can also be used in accordance with the presentinvention, including, but are not limited to, water reducers,accelerators, air entrainment agents, as well as other additives thatare commonly used in the concrete industry.

The mixes of the invention are prepared by homogeneously and uniformlymixing all of the mix ingredients including the Class-F fly ash, Class-Cfly ash, slag, and potassium chloride. Mixing can be accomplished withmixing techniques commonly employed in the concrete mix industry. Theultimate compositions are no more susceptible to undergoing separationduring handling and storage than are ordinary concrete mixes. They canbe transported and stored in the same manner as the ordinary mixes, ascan the individual ingredients. The storage containers should, ofcourse, be closed to protect the contents thereof from weather.

The following examples are given to illustrate the present invention. Itshould be understood that the invention is not limited to the specificconditions or details described in these examples.

The results in the following examples were actually obtained bypreliminarily blending, in each case, the Class-F fly ash, Class-C flyash, slag, and potassium chloride together and combining the blend withthe other mix ingredients. However, the results would be identical ifthe same proportionate amount for each of the component was addedseparately to the remaining mix ingredients and the proportionateamounts of the Class-F fly ash, Class-C fly ash, slag, and potassiumchloride have been expressed in each case in terms of their relativeweight percentages of the particular mix.

EXAMPLE 1

TABLE 1A Setting Time Cement KCl (minutes) Mix # (%) (%) 1 Day PSIInitial Final 1 100 0 2670 230 315 2 98.5 1.5 4060 210 285 3 97 3 4520195 250 4 95.5 4.5 4260 175 235

TABLE 1B Mix # 7 Day PSI 28 Day PSI 1 5780 7660 2 6560 7550 3 6410 72604 6160 6780

In Example 1, the cements which include potassium chloride (Mix #2-4)are compared with the cement without potassium chloride (Mix #1).Samples were tested for compressive strength in accordance with ASTMC-109 and for setting times in accordance with ASTM C-403/C-403M-99.

EXAMPLE 2

TABLE 2A Setting Time Cement Class-F fly KCl (minutes) Mix # (%) ash (%)(%) 1 Day PSI Initial Final 5 70 30 0 1860 290 390 6 70 28.5 1.5 2840225 305 7 70 27 3 3090 215 300 8 70 25.5 4.5 2960 200 275

TABLE 2B Mix # 7 Day PSI 28 Day PSI 5 4310 6030 6 4990 6000 7 4910 58908 4710 5740In Example 2, the cements which include Class-F fly ash and potassiumchloride (Mix #6-8) are compared with the cement with Class-F fly ashonly (Mix #5). Samples were tested for compressive strength inaccordance with ASTM C-109 and for setting times in accordance with ASTMC-403/C-403M-99.

EXAMPLE 3

TABLE 3A Setting Time Cement Class-C fly KCl (minutes) Mix # (%) ash (%)(%) 1 Day PSI Initial Final  9 70 30 0 2080 380 460 10 70 28.5 1.5 3020305 375 11 70 27 3 3500 280 340 12 70 25.5 4.5 3320 255 305

TABLE 3B Mix # 7 Day PSI 28 Day PSI  9 6000 7820 10 5780 7030 11 56306700 12 5480 6380

In Example 3, the cements which include Class-C fly ash and potassiumchloride (Mix #10-12) are compared with the cement with Class-C fly ashonly(Mix #9). Samples were tested for compressive strength in accordancewith ASTM C-109 and for setting times in accordance with ASTMC-403/C-403M-99.

EXAMPLE 4

TABLE 4A Setting Time Cement Class CF KCl (minutes) Mix # (%) fly ash(%) (%) 1 Day PSI Initial Final 13 70 30 0 1960 320 405 14 70 98.5 1.52980 260 335 15 70 97 3 3200 235 300 16 70 95.5 4.5 3190 220 290

TABLE 4B Mix # 7 Day PSI 28 Day PSI 13 5160 6740 14 5410 6430 15 54106190 16 5050 6020

In Example 4, the cements which include Class CF fly ash and potassiumchloride (Mix #14-16) are compared with the cement with Class CF fly ashonly (Mix #13). Samples were tested for compressive strength inaccordance with ASTM C-109 and for setting times in accordance with ASTMC-403/C-403M-99.

Class CF fly ash is the product of a mixture of western and easterncoal. An all-western coal produces Class-C fly ash; and an all-easterncoal produces Class-F fly ash. Because of emissions and environmentalconcerns, power plants may burn a mixture of eastern and western coals.Further, the percentages of eastern and western coals may vary accordingto the needs of the individual power plant. The CF ash used in Example 4is the product of a 50/50 blend of eastern and western coal.

EXAMPLE 5

TABLE 5A Setting Time Cement Slag KCl (minutes) Mix # (%) (%) (%) 1 DayPSI Initial Final 17 70 30 0 2080 245 335 18 70 28.5 1.5 2780 215 285 1970 17 3 3080 195 255 20 70 25.5 4.5 2930 190 240 21 50 50 0 1410 275 36522 49.25 49.25 1.5 1830 230 310 23 48.5 48.5 3 1830 230 310

TABLE 5B Mix # 7 Day PSI 28 Day PSI 17 4910 6750 18 6040 7610 19 62406990 20 5660 6970 21 4120 6500 22 5020 6810 23 5000 6990

In Example 5, the cements which include slag and potassium chloride (Mix#18-20 and 22-23) are compared with cements with slag only (Mix #17 and21). Samples were tested for compressive strength in accordance withASTM C-109 and for setting times in accordance with ASTMC-403/C-403M-99.

The above examples clearly show improved one day strength and settingtimes of concrete by the addition of up to about 5 percent potassiumchloride. The improvement is effective not only for cement, but also formixes comprising industrial by-products such Class-F fly ash, Class-Cfly ash, blast furnace slag, and combinations thereof. The invention,however, is not limited to the conditions illustrated in the examples.

Although certain presently preferred embodiments of the invention havebeen specifically described herein, it will be apparent to those skilledin the art to which the invention pertains that variations andmodifications of the various embodiments shown and described herein maybe made without departing from the spirit and scope of the invention.Accordingly, it is intended that the invention be limited only to theextent required by the appended claims and the applicable rules of law.

1. A settable composition comprising cement, slag, Class-C fly ash, andpotassium chloride.
 2. The composition of claim 1, wherein the cement isPortland cement.
 3. The composition of claim 1, wherein the cement ispresent in an amount of at least about 50 percent by weight based on thetotal weight of the settable composition.
 4. The composition of claim 1,wherein the slag is present in an amount of about 5 percent to about 50percent by weight based on the total weight of the settable composition.5. The composition of claim 1, wherein the potassium chloride is presentin an amount of about 1 percent to about 5 percent by weight based onthe total weight of the settable composition.
 6. The composition ofclaim 1, wherein the cement is present in an amount of at least about 50percent, the slag is present in an amount of about 20 percent to about30 percent, the potassium chloride is present in an amount of about 1percent to about 5 percent, and Class-C fly ash is present in an amountof about 20 percent to about 30 percent, wherein all percentages arebased on the total weight of the settable composition.
 7. A method ofmaking concrete comprising steps of i) mixing the settable compositionof claim 1 with water, sand, and gravel to form a mixture; ii) formingthe mixture into a shape; iii) allowing the mixture to harden to formconcrete.
 8. The method of claim 7, wherein the cement is Portlandcement.
 9. The method of claim 7, wherein the cement is present in anamount of at least about 50 percent by weight based on the total weightof the settable composition.
 10. The method of claim 7, wherein the slagis present in an amount of about 5 percent to about 50 percent by weightbased on the total weight of the settable composition.
 11. The method ofclaim 7, wherein the potassium chloride is present in an amount of about1 percent to about 5 percent by weight based on the total weight of thesettable composition.
 12. The method of claim 7, wherein the cement ispresent in an amount of at least about 50 percent, the slag is presentin an amount of about 20 percent to about 30 percent, and the potassiumchloride is present in an amount of about 1 percent to about 5 percent,and Class-C fly ash is present in an amount of about 20 percent to about30 percent, wherein all percentages are based on the total weight of thesettable composition.
 13. The method of claim 7, wherein the formingstep comprises pouring the mixture into a form prior to allowing themixture to harden.
 14. The composition of claim 1, wherein the Class-Cfly ash is present in an amount of about 20 percent to about 30 percent.15. The method of claim 7, wherein the Class-C fly ash is present in anamount of about 20 percent to about 30 percent.